In recent years there has been a great demand for miniaturization of dielectric elements as electronic circuits reach higher densities, and miniaturization of electronic components such as laminated ceramic capacitors together with increased capacity are rapidly progressing, while the applications thereof are also expanding. Various characteristics are required as this takes place.
For example, medium- and high-voltage capacitors which are used in devices such as engine electric computer modules (ECMs), fuel injection devices, electronic control throttles, inverters, converters, high-intensity discharge (HID) headlamp units, hybrid engine battery control units and digital still cameras often have a rated voltage in excess of 100 V because they are used in circuits for providing a high voltage boost. That is to say, medium- and high-voltage capacitors such as these need a high dielectric constant and high capacitance when a high DC bias is applied.
However, conventional dielectric compositions are designed on the assumption that they will be used when a low DC bias of the order of 1 V/μm is applied, for example. This means that if an electronic component having a dielectric layer comprising a conventional dielectric composition is used when a high DC bias is applied, there is a problem in that the dielectric constant and the capacitance are reduced. This problem becomes more marked the higher the DC bias, especially in laminated ceramic capacitors which have very thin layers, because the dielectric constant and capacitance tend to decrease.
In order to solve the abovementioned problem, Patent Document 1 mentioned below describes a dielectric composition which contains a main component comprising: barium titanate having an alkali metal oxide content of 0.02 wt % or less; at least one compound selected from among europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, and ytterbium oxide; barium zirconate, magnesium oxide and manganese oxide, the main component being represented by the following compositional formula: {BaO}mTiO2+αR2O3+βBaZrO3+γMgO+gMnO (where R2O3 is at least one compound selected from among Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3; and α, β, γ, and g represent a mole ratio and are within the following ranges: 0.001≤α≤0.06, 0.005≤β≤0.06, 0.001<γ0.12, 0.001<g≤0.12, γ+g≤0.13, and 1.000<m≤1.035); and the dielectric composition contains, as an auxiliary component, silicon oxide in an amount of 0.2-5.0 mol as SiO2 equivalent, with respect to 100 mol of the main component.
However, although a dielectric composition such as that described in Patent Document 1 has a relatively large dielectric constant when a DC bias of 5 V/μm is applied, a dielectric composition having a high dielectric constant under an even higher DC bias voltage of the order of 8 V/μm, for example, would be desirable in order to cope with the thinner layers accompanying the miniaturization and higher capacity of medium- and high-voltage capacitors.
In addition, there is a need for a sufficiently large withstand field (e.g., 14 V/μm or greater) under an environment in which a DC bias of the order of 8 V/μm is applied.